Most modem hearing aids are programmable for adaptation to the hearing aid user's needs. Rationales have been developed; which provide a good first approach to the fitting of the hearing aid to the user. The rationales are data sets specifying the transfer function or the gain of the hearing aid over a relevant frequency range.
Some users with severe to profound hearing losses have, however, a special need for adaptation; which goes beyond what can be achieved by means of the traditionally developed rationales. These users often have a relatively normal upper hearing threshold (normally designated the uncomfortable level (UCL)), whereas the lower hearing threshold (HTL) has been significantly offset compared to that of a normal hearing person.
Speech in everyday environments can cover a 70 dB or greater dynamic range. From the softest elements of soft speech to the most intense elements of loud speech, the listener with normal hearing uses most of his/her dynamic range throughout the day. Multi-channel non-linear processing is designed to make use of most—if not all—of this dynamic range available to the patient with sensorineural hearing loss. However, as the hearing loss moves into the severe and then profound ranges, this core assumption needs to be modified, especially for some clients.
The assumption common to the fitting of other hearing losses up to this point is that the ear should be able to make reasonable use of amplified speech information, even when compressed. Given the dramatic nature of the damage in profound hearing loss, this assumption may not always be true. The damage pattern in some ears with profound hearing loss may need a signal that is more linear whereas others may be able to make full use of a signal that is highly compressed.
The objective of the present invention is to provide equipment that can provide an improved initial setting of the hearing aid in order to achieve a faster and better fitting of the hearing aid.